Scientists and engineers often employ seismic surveys for exploration, archeological studies, and engineering projects. Seismic surveys can provide information about underground structures, including formation boundaries, rock types, and the presence or absence of fluid reservoirs. Such information greatly aids searches for water, geothermal reservoirs, and mineral deposits such as hydrocarbons and ores. Oil companies in particular often invest in extensive seismic surveys to select sites for exploratory oil wells.
Conventional seismic surveys employ artificial seismic energy sources such as shot charges, air guns, or vibratory sources to generate seismic waves. The sources, when fired, create a seismic “event”, i.e., a pulse of seismic energy that propagates as seismic waves from the source down into the earth. Faults and boundaries between different formations create differences in acoustic impedance that cause partial reflections of the seismic waves. A seismic sensor array detects and records these reflections for later analysis. Sophisticated processing techniques are applied to the recorded signals to extract an image of the subsurface structure.
The sensor arrays used to detect the seismic waves include hundreds or even thousands of sensors that are arranged in a systematic pattern and linked to data recorders. The sensors arrays require a substantial amount of effort to deploy and re-position throughout the survey process, adding to the time and cost of performing a survey. One remote sensing technology has been proposed elsewhere (See, e.g., U.S. Pat. No. 5,070,483, “Remote Seismic Sensing” to Albert Berni), but to the best of the inventor's knowledge it has not been commercialized and its performance is unknown. Without access to such technologies, seismic explorationists must continue to rely on expensive and time consuming survey techniques.